The present invention relates to improvements in dynamoelectric machines and more particularly to an improved cooling arrangement for such a machine that can be assembled on the outer surface of a dynamoelectric machine housing without damaging the finish thereof.
In certain applications, electric motors are used as direct drive fan motors in heating and air conditioning systems. Generally these motors are not self cooled; and are cooled by air drawn over the motor by the fan. Electric motors often are subject to being operated in high moisture environments especially in such applications as room air conditioners and outdoor condensing units. Accordingly, it has become general practice to design electric motors for such applications having drip-proof or totally enclosed housings to protect internal parts of the electric motor from moisture or water.
Electric motors, of course, include heat generating components; e.g., bearings, stator core, and excitation windings, and when the heat generating components of the motor are effectively enclosed, a major difficulty has been experienced in satisfactorily dissipating the generated heat from the interior of the motor.
If this heat is not effectively removed from the motor, it will have the general effect of increasing the resistance of the windings and the total temperature rise of the motor, thereby producing a marked decrease in the motor performance. Moreover, increased operating temperatures of the motor may adversely affect bearing materials and lubricants and other temperature sensitive motor components; e.g., electrical insulation, which can lose its mechanical and dielectric strengths at high temperatures, eventually resulting in premature motor failure. Therefore it should be apparent that there is a need for a device to minimize excessive temperature rises and thereby reduce motor power losses. Such a device should preferably be a device which can be added to an existing motor design as an auxiliary piece of hardware. Thereby the economics of high volume production for existing motor designs could be retained and the heat dissipation problem could be improved in applications where additional cooling means are required.
In the past, electric motors have been manufactured with a cast outer shell having fins formed therein so that the fins could aid in dissipating some of the heat in the outer housing. However, such motors are expensive and tend to be limited to applications requiring additional cooling aid since the additional expense would not warrant using such a motor in an application not requiring additional cooling. Another auxiliary cooling scheme used in the past was to weld corrogated sheet metal to the outer housing of an electric motor. However, such corrogated fins do not dissipate as much heat as a cast fin dissipates and in addition after the welding was completed the motor would require repainting to restore its outer finish to an acceptable appearance.
Another cooling arrangement that has been suggested in the past was to put an extruded aluminum fin shell around the outer housing of the electric motor. The extruded aluminum fin shells were interlocked to each other and then slid or press fitted onto the outer housing of the electric motor. Press fitting or sliding the extruded aluminum fin shells over the outer housing could damage the finish on the outer surface of the housing which would then have to be retouched to restore an acceptable appearance to the motor's outer housing.
Therefore, it is a principle object of the present invention to provide an improved means for cooling the interior of a dynamoelectric machine by an auxiliary cooling device that is assembled on a fully manufactured dynamoelectric machine.
Another object of this invention is to provide a dynamoelectric machine having an improved cooling arrangement for effectively removing and dissipating the heat, which is generated, from the motor housing.
A still further object of the invention is to provide a dynamoelectric machine having an improved cooling arrangement for transferring heat from the housing of the machine, which improved cooling arrangement can be assembled on the outer housing of the machine without defacing the finish on the outer housing.